1. Field of the Invention
The present invention relates generally to a mixing valve, and more particularly, to a variable flow mixing valve especially well suited for use as a water faucet wherein either of two fluids may be delivered independently, or the two fluids may be mixed in preselected proportions for delivery.
2. Prior Art
Various forms of so-called mixing valves or faucets incorporating mixing valves have been developed for residential and other uses to deliver either of two fluids independently or to mix two fluids for delivery. Valves of this type are ordinarily used to deliver water at cold or hot supply temperatures, or at one or more intermediate temperatures, and at flow rates chosen by the user.
Early mixing valves consisted essentially of cold and hot water valve structures actuated by independent controls, but discharging jointly through a common spout. These dual control valves do not perform an internal mixing function but rather simply discharge regulated flows of cold and hot water through a common spout. A certain amount of skill is required by the user to independently adjust the dual flow controls to deliver water at a desired flow rate and at a desired temperature. Delivering water at a constant intermediate temperature throughout a range of available flow rates has been virtually impossible utilizing these early dual control valves.
More recently, mixing valves employing a single control have been developed. These single control valves typically provide a manually operable lever which is movable in one mode to deliver water at a selected temperature, and in another mode to provide a desired flow rate. Just as dual control valves require a certain amount of operator skill to effect delivery of water at a desired temperature and flow rate, these improved single control valves likewise require a certain amount of operator skill to effect the desired operation. Trial and error positioning of the control is often required to obtain a mixed flow of desired temperature. Those who are unfamiliar with the operation of a particular single control valve often find a substantial amount of trial and error positioning of its control is needed to achieve the desired delivery rate and temperature.
The referenced Mixing Valve Patent presents a further advance in mixing valve art. In the type of mixing valve described in this Patent, separate finger-operated controls are provided for supplying unmixed flows of cold and hot water. Additionally, one or more finger-operated controls are provided for supplying one or more mixed flows at a preselected intermediate temperature or temperatures. By this arrangement, each of the finger-operated controls regulates the delivery of water at a different delivery temperature. Delivery flow rate is established by positioning the proper control along its path of movement. Selection of the intermediate temperature or temperatures is effected by setting one or more flow restriction controls to properly proportion the relative rates of flow of cold and hot water which are supplied to each mixing chamber.
A "trickle flow" approach is described in the referenced Mixing Valve Patent for maintaining a constant temperature delivery of mixed water throughout an available range of flow rates. A primary valve element controls the admission of separate flows of cold and hot water to a mixing chamber. A secondary valve element regulates the flow of mixed fluid from the mixing chamber. The secondary valve element is described as never closing completely and as functioning in concert with the primary valve element to assure the presence of a properly stabilized flow through the mixing chamber. The approach described in the referenced Mixing Valve Patent has been improved upon through the development of the present invention.
While the arrangement described in the referenced Mixing Valve Patent provides a rather easily serviceable unit which is producible as a durable structure at comparatively low cost, it does not provide a low cost operational "cartridge" which can be disposed of and readily replaced in the event the valve requires service.
A problem not addressed by the Mixing Valve Patent is deterioration of the secondary valve element due to repeated flexures. Moreover, some of the parts of the valve structure of the referenced Mixing Valve Patent have been found to require more complex fabrication techniques than was initially thought necessary.
Still another problem not addressed by the referenced Mixing Valve Patent is the need to provide for ease of adjusting the predetermined temperature or temperatures of the mixed flow or flows through a wide range of temperatures without having to remove a decorative cover or to utilize tools.